Encapsulated visible light absorbing dye polyurethane dispersion

ABSTRACT

The present disclosure provides an encapsulated visible light absorbing dye dispersion, and the process for producing the same. The present disclosure further provides an inkjet ink comprising an ink vehicle and an encapsulated visible light absorbing dye dispersion thereof, and the process for producing the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly owned and co-pending, U.S. patentapplication Ser. No. ______ (not yet assigned) entitled “EncapsulatedFluorescent and Photochromic Dye Polyurethane Dispersion” to JeffreyBanning et al., electronically filed on the same day herewith (AttorneyDocket No. 20131661-430294); U.S. patent application Ser. No. ______(not yet assigned) entitled “Encapsulated Titanium Dioxide, FluorescentPigments, and Pigmented Polyurethane Dispersion” to Jeffrey Banning etal., electronically filed on the same day herewith (Attorney Docket No.20131658-430291); U.S. patent application Ser. No. ______ (not yetassigned) entitled “Pigmented Polyurethane Dispersion” to JeffreyBanning et al., electronically filed on the same day herewith (AttorneyDocket No. 20131663-430295); the entire disclosures of which areincorporated herein by reference in its entirety.

INTRODUCTION

Polyurethane dispersions have been employed as carriers in aqueous inkjet inks, for example, U.S. Pat. No. 5,700,851, and aqueous writinginks, for example, U.S. Pat. No. 5,637,638, which are entirelyincorporated by reference herein. The dispersions described in thesepatents employed reactive polymeric colorants that are built into thepolyurethane backbone of the molecule by covalent bonding, and act asthe source of coloration of the final ink.

Visible light absorbing dyes are highly sought after for ink and coatingapplications.

However, encapsulating or incorporating visible light absorbing dyes thelatex, in an emulsion polymerization, is not a trivial endeavor. This isbecause, during an emulsion polymerization, the visible light absorbingdye must satisfy the following requirements (1) be soluble in themonomers used in the emulsion polymerization, (2) be captured in amonomer micelle as polymerization takes place inside the micelle, and(3) be stable to the free radical polymerization environment. Manyorganic visble light absorbing dyes are not stable to such environmentsand their colors are subsequently destroyed. Typically, even if theencapsulated visble light absorbing dye survives the entirepolymerization process, it is often not stable to the free radicalenvironment at the end of the process when all the excess monomers aredestroyed under oxidative or reductive conditions. The encapsulation ofa visble light absorbing dye into a polyurethane dispersion circumventsall of these problems.

It is important that ink compositions comprising visible light absorbingdye dispersion remain stable, not only in storage but also over repeatedjetting cycles. Therefore, a need exists for a method to encapsulatevisible visible light absorbing dyes into the latex, and to provide ahighly stable visible light absorbing dye polyurethane dispersion, whichmay be used for ink-jet applications.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a water-in-oil dispersion of a mixture of water and aneutralized prepolymer containing a visible light absorbing dyeaccording to certain embodiments of the present disclosure.

FIG. 2 shows an oil-in-aqueous dispersion of a mixture of water and aneutralized prepolymer containing a visible light absorbing dye afterhigh speed spinning according to certain embodiments of the presentdisclosure.

FIG. 3 shows a close up view of a single visible light absorbing dyedispersion particle in water according to certain embodiments of thepresent disclosure.

FIG. 4 shows a close up view of a single visible light absorbing dyedispersion particle after the addition of a chain extender dispersionaccording to certain embodiments of the present disclosure.

SUMMARY OF THE INVENTION

The disclosure provides an encapsulated visible light absorbing dyedispersion comprising a polyurethane dispersion that is the reactionproduct of: (a) a urethane prepolymer, the urethane prepolymer being thecatalyzed reaction product of: (i) a polyol; (ii) a polyisocyanate; and(iii) an internal surfactant; (b) a neutralizing agent; and (c) a chainextender; and a visible visible light absorbing dye, wherein the visiblevisible light absorbing dye is not reactive towards the polyisocyanate.

In further embodiments, the disclosure provides an encapsulated visiblelight absorbing dye dispersion comprising: a polyurethane dispersionthat is the reaction product of: (a) a urethane prepolymer that is thecatalyzed reaction product of: (i) a polyol; (ii) a polyisocyanate; and(iii) an internal surfactant; wherein the stoichiometric equivalentmolar ratio of internal surfactant to polyol is from about 0.5 to about2.0 and the stoichiometric equivalent molar ratio of NCO groups to totalOH groups in the prepolymer is from about 1.2 to about 2.0; (b) aneutralizing agent; and (c) a chain extender; and an aqueous visiblelight absorbing dye dispersion comprising a visible visible lightabsorbing dye that is not reactive towards the polyisocyanate, whereinthe visible visible light absorbing dye is not reactive towards thepolyisocyanate, further wherein the encapsulated visible light absorbingdye dispersion has an average particle size of from about 20 nm to about900 nm, a viscosity of from about 2 to about 150 cps at roomtemperature, and a surface tension of from about 15 to about 65 dyn atroom temperature.

In embodiments, the disclosure also provides an ink jet ink compositioncomprising an encapsulated visible light absorbing dye dispersioncomprising: a polyurethane dispersion that is the reaction product of:(a) a urethane prepolymer that is the catalyzed reaction product of: (i)a polyol; (ii) a polyisocyanate; and (iii) an internal surfactant; (b) aneutralizing agent; and (c) a chain extender; and a visible visiblelight absorbing dye, wherein the visible visible light absorbing dye isnot reactive towards the polyisocyanate.

DETAILED DESCRIPTION

As used herein, the term “dispersion” means a two phase system where onephase consists of finely divided particles (often in the colloidal sizerange) distributed throughout a bulk substance, the particles being thedispersed or internal phase and the bulk substance the continuous orexternal phase. The bulk system is often an aqueous system.

As used herein, the term “PUD”” means the polyurethanes dispersionsdescribed herein.

As used herein, the term “DMPA” means dimethylol propionic acid.

Disclosure provides an encapsulated visible light absorbing dyedispersion including a polyurethane dispersion and an aqueous visiblelight absorbing dye dispersion including a visible visible lightabsorbing dye that is unreactive towards any reagent/or precursor of theurethane prepolymer (i.e., the polyol, the polyisocyanate, and/or theinternal surfactant). The polyurethane dispersion of the disclosure is areaction product of (a) a urethane prepolymer, (b) a neutralizing agent,and (c) a chain extender, where the urethane prepolymer is prepared from(i) a polyol, (ii) a polyisocyanate, and (iii) an internal surfactant.

When preparing the encapsulated visible light absorbing dye dispersionof the present disclosure, a visible light absorbing dye may beincorporated, or encapsulated, into the polyurethane dispersion byadding/dissolving the visible light absorbing dye to the pre-polymerjust before water is added during the formation of the polyurethanedispersion, hence, prior to the addition of a chain extender.

The preparation of encapsulated visible light absorbing dye dispersionrequires a viscous prepolymer being first formed, and then the visiblelight absorbing dye being added after the pre-polymer has been formed.The visible light absorbing dyes of the disclosure are immiscible inwater. Therefore, if such dyes are added to the polyurethanesdispersions after they have been made, the dyes would simply “float” inthe water portion of the latex. In the present disclosure, the dyes areadded to the prepolymer or the components that are reacted to make theprepolymer (i.e., polyisocyanate, polyol & internal surfactant), as thedyes are soluble in these organics.

In certain embodiments, the encapsulated visible light absorbing dyedispersion may be prepared by a process including preparing a urethaneprepolymer, dissolving a visible light abosorbing dye into thisprepolymer; reacting the urethane prepolymer with a neutralizing agent;adding water to the neutralized prepolymer to form an aqueous dispersionof the neutralized prepolymer; and reacting the aqueous dispersion ofthe neutralized prepolymer with a chain extender thereby producing anencapsulated visible light absorbing dye dispersion, wherein the step ofpreparing a urethane prepolymer include adding a visible visible lightabsorbing dye to the reaction mixture. For example, the visible lightabsorbing visible light absorbing dye may be added to the mixture ofpolyol, polyisocyanate, and internal surfactant in the presence of acatalyst.

In certain embodiments, the encapsulated visible light absorbing dyedispersion may be prepared by a process including preparing a urethaneprepolymer; adding/dissolving a visible light absorbing dye to theurethane prepolymer; reacting the urethane prepolymer with aneutralizing agent to form a neutralized prepolymer; adding water to theneutralized prepolymer to form an aqueous dispersion of the neutralizedprepolymer; and reacting the aqueous dispersion of the neutralizedprepolymer with a chain extender thereby producing an encapsulatedvisible light absorbing dye dispersion.

In certain embodiments, the encapsulated visible light absorbing dyedispersion may be prepared by a process including preparing a urethaneprepolymer; reacting the urethane prepolymer with a neutralizing agentto form a neutralized prepolymer; adding a visible light absorbing dyeto the neutralized prepolymer; adding water to the neutralizedprepolymer to form an aqueous dispersion of the neutralized prepolymer;and reacting the aqueous dispersion of the neutralized prepolymer with achain extender thereby producing an encapsulated visible light absorbingdye dispersion.

The urethane prepolymer can be prepared by reacting a polyol, apolyisocyanate, and an internal surfactant in the presence of acatalyst. The internal surfactant may be dissolved in an organicsolvent, such as NMP, DMF, or other polar aprotic solvents, prior to theaddition to the polyol and polyisocyante.

Generally, the stoichiometric equivalent molar ratio of internalsurfactant to polyol may be from about 0.5 to 2, from 0.75 to 1.75, orfrom about 1 to about 1.5, the stoichiometric equivalent molar ratio ofNCO groups to total OH groups in the prepolymer may be from about1.0-3.0, from about 1.25 to 2.5, or form about 1.5 to about 2.0. It isdesired to have a high internal surfactant to polyol ratio and a low NCOgroup to OH group ratio. Typically, the urethane prepolymer reaction iscarried out at about 70° C. to about 100° C. for about 1 to about 5hours until the theoretical isocyanate content, which can be determinedby, e.g., the di-n-butylamine titration method, is reached to form anurethane prepolymer (isocyanate-terminated) containing an internalsurfactant therein.

The urethane prepolymer (isocyanate terminated prepolymer containing aninternal surfactant therein) can be neutralized with a neutralizingagent, such as a trialkylamine, e.g., triethylamine. The amount ofneutralizing agent used may be dependent upon the amount of internalsurfactant present in the urethane prepolymer, and ranges from about 5%to about 100% , from about 10% to about 90% or from about 20% to about70% of the quantity of internal surfactant. This neutralization stepallows the urethane prepolymer to be dispersible by neutralizing thefunctional groups of the urethane prepolymer. In one embodiment, thecarboxylic acid sites on the internal surfactants may be neutralizedthereby forming a salt, such as —CO₂ ⁻HN⁺R₃, where R is a lower alkylgroup.

The neutralized prepolymer, typically, has an average weight molecularweight (MW) of from about 1,000 to about 20,000, from about 3,000 toabout 15,000, or from about 5,000 to about 10,000. Water 1, e.g.,deionized (DI) water, can be added to the neutralized prepolymer 3 whichcontains visible light absorbing dye 2 which can be added during theformation of the prepolymer or after the formation of the prepolymer butprior to the addition of the neutralizing agent. The amount of water inthe aqueous dispersion is based on the desired percentage of solids inthe final polyurethane dispersion, which may be in amount of from about1.0 to about 99 percent, from about 20 to about 80 or from about 35 toabout 60 percent based on the total weight of the aqueous dispersion.The aqueous dispersion usually starts out as a “water-in-oil” dispersionthe moment the water is added under dispersion conditions. FIG. 1 showsa “water-in-oil” dispersion when water is first added to the neutralizedprepolymer. During the dispersion process, the mixture (i.e., water andthe neutralized prepolymer 3) may be spinned at high speed (e.g.,5,000-10,000 rpms) and the “water-in-oil” dispersion may be converted toan “oil-in-water” dispersion. The dispersion can be accomplished byspinning a blade, such as a dispersion blade 4. The effect of employinga dispersion blade at high speed imparts energy into the system todisperse rather than to mix. At this point, the particle size of thefinal encapsulated visible light absorbing dye dispersion may bedetermined. FIG. 2 shows an “oil-in-water” dispersion, where theneutalized prepolymer 3 is suspended in the water. Inside a droplet ofthe neutalized prepolymer 3, the terminals (i.e., free —NCO groups) ofthe neutralized prepolymer are at the inside surface of the droplet. Inone embodiment of the disclosure, FIG. 3 shows a close up view of asingle dispersion particle in water, where DMPA is employed as the theinternal surfactant.

A chain extender such as a suitable diamine, triamine, diol or a triol,may be then added to increase the average weight molecular weight of thepolyurethane dispersion by using an amount stoichiometrically equivalentto from about 60 to about 100 percent of the amount of prepolymer, orfrom about 85 to about 95 percent of the amount of the prepolymer. Theaverage weight molecular weight of the polyol employed and theparticular chain extender used can impact the adhesion of the ink to thefinal receiving substrate. The chain extender may diffuse or migrateinto the particles of the dispersion and react with the terminated freeisocyanate groups of the neutralized prepolymer, and thus extend themolecular weight of the polyurenthane polymer and form ureas in theprocess. In one embodiment of the disclosure, FIG. 4 shows a close upview of a single dispersion particle after the addition of a chainextender, e.g., ethylene diamine in water, where DMPA is employed as thethe internal surfactant.

Examples of the chain extender suitable for use in the presentdisclosure include diamines such as ethylenediamine, 1,2-propanediamine,1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine,isophoronediamine, 4,4′-dicyclohexylmethanediamine,3,3′-dimethyl-4,4′-dicyclohexylmethanediamine, and1,4-cyclohexanediamine; diamines containing one primary amino group andone secondary amino group such as N-hydroxymethylaminoethylamine,N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine,N-ethylaminoethylamine, and N-methylaminopropylamine; polyamines such asdiethylenetriamine, dipropylenetriamine, and triethylenetetramine. Inone embodiment, the chain extender includes ethylene diamine.

Any suitable amounts of prepolymer, neutralizing agent, water and chainextender may be added to the urethane prepolymer as long as a stablepolyurethane dispersion is formed.

As a stirring/dispersing device for dispersing pigments, for example,various known dispensers such as a high speed impeller disc, anultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, aball mill, a roll mill, a sand mill, a sand grinder, a dyno mill,dispermat, an SC mill, a nanomizer, or the like can be used.

The encapsulated visible light absorbing dye polyurethane dispersion isthen combined with an aqueous medium, at least one humectant, andoptionally at least one plasticizer.

The encapsulated visible light absorbing dye dispersion of the presentdisclosure may have an average dispersion particle size (i.e., particlediameter) of from about 20 nm to about 900 nm, from about 30 nm to about600 nm, or from about 50 nm to about 100 nm. This size range permits theparticles and the resultant ink in which they are dispersed to overcomesettling and stability/dispersing problems. The average particlediameter can be measured by various methods, for example, they can bemeasured using a particle analyzer UPA 150 manufactured by Nikkiso Co.,Ltd.

The encapsulated visible light absorbing dye dispersion of the presentdisclosure may have a viscosity of from about 2 to about 150 cps, fromabout 10 to about 100 cps, or from about 20 to about 80 cps at roomtemperature. The encapsulated visible light absorbing dye dispersion ofthe present disclosure may have a surface tension of from about 15 toabout 65 dyn, from about 25 to about 60 dyn, or from about 35 to about55 dynes, at room temperature.

The visible light absorbing dye content of the encapsulated visiblelight absorbing dye dispersion of the present disclosure may be in therange of from about 0.1 to about 30 percent, from about 1.0 to about 15percent, or from about 2.0 to about 5.0 percent by weight of theencapsulated visible light absorbing dye dispersion.

The visible light absorbing dyes of the present disclosure areunreactive towards any reagent/or precursor of the urethane prepolymer(i.e., the polyol, the polyisocyanate, and the internal surfactant).Particularly, the pigments do not contain any non-phenolic hydroxylgroup nor aliphatic primary or secondary amines, but may include aphenolic hydroxyl group and/or a tertary amine in which one of the threesubstituents is an aromatic ring.

The visible light absorbing dyes used in the present disclosure may havea maximum absorphtion wavelength in a range of about 400 to about 700nm. examples of visible visible light absorbing dyes include Color Index(CI) Solvent Visible light absorbing dyes, Disperse Visible lightabsorbing dyes, modified Acid and Direct Visible light absorbing dyes,Basic Visible light absorbing dyes, Sulphur Visible light absorbingdyes, Vat Visible light absorbing dyes, and the like. Examples ofsuitable visible light absorbing dyes include Neozapon Red 492 (BASF);Orasol Red G (Pylam Products); Direct Brilliant Pink B (Oriental GiantDyes); Direct Red 3BL (Classic Dyestuffs); Supranol Brilliant Red 3BW(Bayer AG); Lemon Yellow 6G (United Chemie); Light Fast Yellow 3G(Shaanxi); Aizen Spilon Yellow C-GNH (Hodogaya Chemical); BemachromeYellow GD Sub (Classic Dyestuffs); Cartasol Brilliant Yellow 4GF(Clariant); Cibanone Yellow 2G (Classic Dyestuffs); Orasol Black RLI(BASF); Orasol Black CN (Pylam Products); Savinyl Black RLSN (Clariant);Pyrazol Black BG (Clariant); Morfast Black 101 (Rohm & Haas); DiaazolBlack RN (ICI); Thermoplast Blue 670 (BASF); Orasol Blue GN (PylamProducts); Savinyl Blue GLS (Clariant); Luxol Fast Blue MBSN (PylamProducts); Sevron Blue 5GMF (Classic Dyestuffs); Basacid Blue 750(BASF); Keyplast Blue (Keystone Aniline Corporation); Neozapon Black X51(BASF); Classic Solvent Black 7 (Classic Dyestuffs); Sudan Blue 670(C.I. 61554) (BASF); Sudan Yellow 146 (C.I. 12700) (BASF); Sudan Red 462(C.I. 26050) (BASF); C.I. Disperse Yellow 238; Neptune Red Base NB543(BASF, C.I. Solvent Red 49); Neopen Blue FF-4012 (BASF); Fatsol Black BR(C.I. Solvent Black 35) (Chemische Fabriek Triade BV); Morton MorplasMagenta 36 (CI Solvent Red 172); metal phthalocyanine colorants such asthose disclosed in U.S. Pat. No. 6,221,137, the disclosure of which istotally incorporated herein by reference, and the like. Polymeric dyescan also be used, such as those disclosed in, for example, U.S. Pat. No.5,621,022 and U.S. Pat. No. 5,231,135, the disclosures of each of whichare herein entirely incorporated herein by reference, and commerciallyavailable from, for example, Milliken & Company as Milliken Ink Yellow869, Milliken Ink Blue 92, Milliken Ink Red 357, Milliken Ink Yellow1800, Milliken Ink Black 8915-67, uncut Reactint Orange X-38, uncutReactint Blue X-17, Solvent Yellow 162, Acid Red 52, Solvent Blue 44,and uncut Reactint Violet X-80.

Typical dyes, classified in the Color Index under the title “DisperseDyes,” generally belong to groups comprising azo, anthraquinone,phthalocyanine, indophenol, indoaniline, perinone, quinophthalone,acridine, xanthone, diazine, and oxazine dyes.

Specific examples of visible light absorbing dyes include Solvent Blue25, Solvent Yellow 43, Disperse Blue 359, Disperse Yellow 54, DisperseRed 60.

As used herein, the term “polyol” is intended to include materials thatcontain two or more hydroxyl groups, e.g., diol, triol, tetraol, etc.The average weight molecular weight of the polyol may be in the range offrom about 60 to about ×10,000×, from about ×500× to about 5000, or fromabout ×1000× to about ×2000×. Non-limiting examples of polyols includediols, triols, polyether polyols, polyacrylate polyols, polyesterpolyols, polycarbonate polyols, and combinations thereof. Suitablepolyether polyol include, but are not limited to, polytetramethyleneether glycol (PTMEG), polyethylene propylene glycol, polyoxypropyleneglycol, and mixtures thereof. The hydrocarbon chain can have saturatedor unsaturated bonds and substituted or unsubstituted aromatic andcyclic groups. Suitable polyacrylate polyols include, but are notlimited to, glycerol 1,3-diglycerolate diacrylate Suitable polyesterpolyols include, but are not limited to, polyethylene adipate glycol;polybutylene adipate glycol; polyethylene propylene adipate glycol;o-phthalate-1,6-hexanediol; poly(hexamethylene adipate) glycol; andmixtures thereof. Suitable polycarbonate polyols include, but are notlimited to, poly(polyTHFcarbonate)diol.

As used herein, the term “polyisocyanate” is intended to includematerials that contain two or more isocyanate groups. The average weightmolecular weight of the polyisocyanate may be in the range of from about140 to about 1000, from about 168 to about 262, or from about 222 toabout 680. Suitable polyisocyanates include diisocyanates,triisocyanates, copolymers of a diisocyanate, copolymers of atriisocyanate, polyisocyanates (having more than three isocyanatefunctional groups), and the like, as well as mixtures thereof. Examplesof diisocyanates include isophorone diisocyanate (IPDI); toluenediisocyanate (TDI); diphenylmethane-4,4′-diisocyanate (MDI);hydrogenated diphenylmethane-4,4′-diisocyanate (H12MDI); tetra-methylxylene diisocyanate (TMXDI); hexamethylene-1,6-diisocyanate (HDI);hexamethylene-1,6-diisocyanate; napthylene-1,5-diisocyanate;3,3′-dimethoxy-4,4′-biphenyldiisocyanate;3,3′-dimethyl-4,4′-bimethyl-4,4′-biphenyldiisocyanate; phenylenediisocyanate; 4,4′-biphenyldiisocyanate; trimethylhexamethylenediisocyanate; tetramethylene xylene diisocyanate;4,4′-methylenebis(2,6-diethylphenyl isocyanate);1,12-diisocyanatododecane; 1,5-diisocyanato-2-methylpentane;1,4-diisocyanatobutane; dimer diisocyanate and cyclohexylenediisocyanate and its isomers; uretidione dimers of HDI; and the like, aswell as mixtures thereof. Examples of triisocyanates or theirequivalents include the trimethylolpropane trimer of TDI, and the like,isocyanurate trimers of TDI, HDI, IPDI, and the like, and biuret trimersof TDI, HDI, IPDI, and the like, as well as mixtures thereof. Examplesof higher isocyanate functionalities include copolymers of TDI/HDI, andthe like, and MDI oligomers, as well as mixtures thereof.

Suitable internal surfactants include both anionic and cationic internalsurfactants. These include sulfonate diamines and diols, and dihydroxycarboxylic acids. In one embodiment, the internal surfactant isα,α-dimethylolpropionic acid (DMPA).

Any conventional urethane forming catalyst can be used in theprepolymer-forming reaction. Suitable urethane reaction catalyst,include, but are not limited to, dibutyl tindilaurate, bismuthtris-neodecanoate, cobalt benzoate, lithium acetate, stannous octoate,triethylamine, or the like.

The encapsulated visible light absorbing dye dispersions of the presentdisclosure may be used in inkjet inks. The inkjet inks of the presentinvention can be prepared by diluting the encapsulated visible lightabsorbing dye dispersion of the present invention with water or anaqueous solvent that contains water, and adding thereto other optionaladditives, e.g., humectant, plasticizier, contuctibity agents,defoamers, anti-oxidants, corrosion inhibitors, bacteriocides, pHcontrol agents, if necessary.

The ink jet ink compositions may include a humectant. Examples ofhumectants include, but are not limited to, alcohols, for example,glycols such as 2,2′-thiodiethanol, glycerol, 1,3-propanediol,1,5-pentanediol, polyethylene glycol, ethylene glycol, diethyleneglycol, propylene glycol and tetraethylene glycol; pyrrolidones such as2-pyrrolidone; N-methyl-2-pyrrolidone; N-methyl-2-oxazolidinone; andmonoalcohols such as n-propanol and iso-propanol. The humectant may bepresent in an amount from about 2% to about 20%, or from about 4% toabout 10% by weight of the ink composition.

The ink jet ink compositions may include a plasticizer. Examples ofplasticizers include, but are not limited to, aliphatic polyols,phthalate esters (such as 1,6-hexane diol and dioctylphthalate), andother urethane compatible plasticizers.

The ink jet ink compositions may also include other components to impartcharacteristics desirable for ink jet printing applications. Theseoptional components include conductivity agents, defoamers,anti-oxidants and corrosion inhibitors which improve ink manufacturingand printer performance; bacteriocides, which prevent bacterial attackthat fouls ink manufacturing equipment and printers; and pH controlagents, which insure that the components of the ink composition remainsoluble throughout the operable range of water contents as well asthroughout the period of storage and use.

The ink jet ink compositions of the present disclosure have a highdegree of transparency and brightness. The inks of the presentdisclosure may have a surface tension in the range of about 20 dynes/cmto about 70 dynes/cm, or in the range 30 dynes/cm to about 50 dynes/cm;a viscosity in the range of about 1.0 to about 10.0, or about 1.0 toabout 5.0 centipoise at room temperature.

The encapsulated visible light absorbing dye dispersion particles remainstabilized or dispersed in a liquid carrying medium in the ink having apH of from about 4 to about 10, from about 5 to about 9, or from about 6to about 8.

EXAMPLES

The following Examples further illustrate the present invention. Allparts and percentages are by weight and all temperatures are degreesCelsius unless explicitly stated otherwise.

Example 1 Preparation of Neutralized Dyed Pre-Polymer

Pre-Dissolved DMPA/NMP Solution:

Into a 50 ml flask equipped with a Teflon coated stir magnetic was added9.75 g of 2,2-bis(hydroxymethyl) propionic acid (DMPA, MW=134, availablefrom Adrich Chemical of Milwaukee, Wis.) and 15.6 g ofN-methylpyrrolidone (NMP). The mixture was heated at 70° C. withstifling until the DMPA was completely dissolved.

Pre-Polymer Formation:

Into a 1 L kettle equipped with a Trubore stirrer and Teflon stirpaddle, temperature controller, 100 mL constant pressure addition funneland N₂ inlet was charged 72.76 g pre-melted Terathane® 2000 (averageMn=2000 poly(tetrahydrofuran), available from Simga-Aldrich). The kettlewas secured in a bracket and the bottom ⅓ of the kettle was submerged ina 70° C. oil bath, and the contents were stirred for 15 minutes. Thepre-dissolved DMPA/NMP solution was added to the kettle. After thecontents were stirred for about 15 minutes, 42.4 g of isopheronediisocyanate (IPDI, MW=222, available from Huls America, Inc. ofPiscataway, N.J.) was added to the kettle drop-wise through an additionfunnel over about 30 minutes. A slight exotherm was observed. Thereaction mixture was continued to be heated at 70° C. with stirring forabout 3 hours and 45 minutes.

Example 2 Neutralization and Incorporation of Visible Light Absorbingdye in Polyurethane Dispersion:

The resulting mixture was added a) 0.5 g of Solvent Blue 25 in 5 g ofNMP, b) 2 g of Solvent Yellow 43 [a cyan dye], c) 2 g Disperse Blue 359[a cyan colored copper phthalocyanine dye], d) 1 g Disperse Yellow 54,or e) 2 g Disperse Red 60 [a red-magenta dye], and stirred for severalminutes, followed by addition of about 7.35 g of triethylamine (MW=101)with continuous stirring and heating at 70° C. After stirring andheating for about 15 minutes the neutralized pre-polymer was ready to bedispersion. The kettle containing the neutralized pre-polymer wastransferred to the dispersing apparatus with the dispersion blade about0.25 inch below the surface of the neutralized pre-polymer.

To the neutralized visible light absorbing dyed pre-polymers obtainedabove were each added 245 mL of chilled (˜5° C.) deionized water. Theresulting mixtures were dispersed at the highest speed (approximately7,500 rpms) with an IKA® Crushing Disperser for about 15 seconds. A longwood tongue depressor was employed to scrape off the un-dispersedpre-polymer stucked on the wall of the kettle. The un-dispersedpre-polymer was placed onto the bottom of the blade of the IKA® CrushingDisperser and dispersed again for about 10 seconds at the highest rpmsetting. Aqueous visible light absorbing dye containing dispersions ofthe neutralized propolymer were obtained.

Example 3 Chain Extension

To the aqueous visible light absorbing dye dispersion of the neutralizedpropolymers obtained in Example 2 was each added dropwise an ethylenediamine solution (4.9 g ethylene diamine/10 g distilled water) overabout 5 minutes. After stifling for about 1 hour, the resulting mixturewas transferred to a 32 oz glass jar, capped and stored for at least 72hours. At the end of the 72 hours, five different encapsulated visiblelight absorbing dye dispersions were obtained.

Example 4 Analysis and Measurments

Approximately 20 g of each of the encapsulated visible light absorbingdye PU-dispersions obtained in Example 3 was poured into a 100 mm×10 cmpetri dish top or bottom and allowed to dry/coalesce over a 48 hourperiod. The samples were pealed out of the Petri dish yielding a coloredurethane disc/film. The color of the urethane disc is described in Table1.

TABLE 1 Visible light absorbing dye Appearance of Polyurethane Films ofExample 4 a) Solvent Blue 25 Cyan colored b) Solvent Yellow 43 Yellowcolored c) Disperse Blue 359 Cyan colored. Some solids settled over timewhich appeared to be un-encapsulated visible light absorbing dye. d)Disperse Yellow 54 Yellow colored. Some solids settled over time whichappeared to be un-encapsulated visible light absorbing dye. e) DisperseRed 60 Red colored. Some solids settled over time which appeared to beun-encapsulated visible light absorbing dye.

The viscosity (cps) and surface tension of the encapsulated pigmentdispersion containing a) Solvent Blue 25 at various concentrationsobtained from Example 3 were measured and the data are shown in Table 2.

TABLE 2 PUD/water ratio CYAN-PUD 100 75/25 50/50 25/75 Viscosity at roomtemperature (cps) 28.83 6.25 2.92 1.78 Surface tension (dyn/cm) at room44.05 temperature

Example 5 Preparation of Aqueous Ink-Jet Inks

Into three separate 2-oz jars was each charged 10 g of a differentencapsulated visible light absorbing dye dispersion obtained fromExample 4, and 2 g of 0.1M pH8 K₂HPO₄/KH₂PO₄ buffer and 8 g DI water.The contents were stirred for about 2 minutes.

The resulting inks were loaded onto three separate empty ink cartridges,and were printed out on an EPSON WF-3540 printer. Xerox 4200 paper wasused.

1. An encapsulated visible light absorbing dye dispersion consistingessentially of: a polyurethane dispersion that is the reaction productof: (a) a urethane prepolymer having an average weight molecular weightof from about 1,000 to about 20,000, the urethane prepolymer being thecatalyzed reaction product of: (i) a polyol; (ii) a polyisocyanate; and(iii) an internal surfactant; (b) a neutralizing agent; and (c) a chainextender selected from the group consisting of diamines, triamines, andcombinations thereof; and a visible light absorbing dye, wherein thevisible light absorbing dye is not reactive towards the polyisocyanate.2. The encapsulated visible light absorbing dye dispersion of claim 1having an average dispersion particle size of from about 20 nm to about900 nm.
 3. The encapsulated visible light absorbing dye dispersion ofclaim 1 having a viscosity of from about 2 to about 150 cps at roomtemperature.
 4. The encapsulated visible light absorbing dye dispersionof claim 1, wherein the stoichiometric equivalent molar ratio ofinternal surfactant to polyol is from about 0.5 to about 2.0 and thestoichiometric equivalent molar ratio of NCO groups to total OH groupsin the prepolymer is from about 1.2 to about 2.0.
 5. The encapsulatedvisible light absorbing dye dispersion of claim 1, wherein the visiblelight absorbing dye is present in the amount of from about 0.1 to about30 percent by weight of the encapsulated visible light absorbing dyedispersion.
 6. The encapsulated visible light absorbing dye dispersionof claim 1, wherein the visible light absorbing dye has an averagevisible light absorbing dye particle size of from about 20 nm to about900 nm.
 7. The encapsulated visible light absorbing dye dispersion ofclaim 1, wherein the polyol is selected from the group consisting ofpolyether polyols, polyester polyols, polycarbonate polyols,silicone-based polyols and combinations thereof.
 8. The encapsulatedvisible light absorbing dye dispersion of claim 1, wherein thepolyisocyanate is selected from the group consisting of aliphatic,cycloaliphatic, aromatic and heterocyclic polyisocyanates andcombinations thereof.
 9. The encapsulated visible light absorbing dyedispersion of claim 1, wherein the internal surfactant is selected fromthe group consisting of anionic internal surfactants, cationic internalsurfactants and combinations thereof.
 10. The encapsulated dyedispersion of claim 1, wherein the internal surfactant comprisesdimethylopropionic acid.
 11. The encapsulated visible light absorbingdye dispersion of claim 1, wherein the neutralizing agent comprisestrialkylamine.
 12. (canceled)
 13. The encapsulated visible lightabsorbing dye dispersion of claim 1, wherein the encapsulated visiblelight absorbing dye dispersion is obtained by the process comprises:preparing a urethane prepolymer; reacting the urethane prepolymer with aneutralizing agent; adding an aqueous dispersion to the neutralizedprepolymer to form an aqueous dispersion of the neutralized prepolymer;and reacting the aqueous dispersion of the neutralized prepolymer with achain extender thereby producing an encapsulated visible light absorbingdye dispersion; wherein the process further includes a step of adding avisible visible light absorbing dye which occurs prior to reacting theaqueous dispersion of the neutralized prepolymer with a chain extender,wherein the visible visible light absorbing dye is not reactive towardsthe polyisocyanate.
 14. (canceled)
 15. The encapsulated visible lightabsorbing dye dispersion of claim 1, wherein a step of adding a visiblelight absorbing dye occurs during the step of preparing a urethaneprepolymer.
 16. The encapsulated visible light absorbing dye dispersionof claim 1, wherein a step of adding a visible light absorbing dyeoccurs after reacting the urethane prepolymer with a neutralizing agentand before adding an aqueous dispersion to the neutralized prepolymer.17. The encapsulated visible light absorbing dye dispersion of claim 1,wherein a step of adding a visible light absorbing dye occurs afteradding an aqueous dispersion to the neutralized prepolymer to form anaqueous dispersion of the neutralized prepolymer and before reacting theaqueous dispersion of the neutralized prepolymer with a chain extender.18. An encapsulated visible light absorbing dye dispersion consistingessentially of: a polyurethane dispersion that is the reaction productof: (a) a urethane prepolymer having an average weight molecular weightof from about 1,000 to about 20,000 that is the catalyzed reactionproduct of: (i) a polyol; (ii) a polyisocyanate; and (iii) an internalsurfactant; wherein the stoichiometric equivalent molar ratio ofinternal surfactant to polyol is from about 0.5 to about 2.0 and thestoichiometric equivalent molar ratio of NCO groups to total OH groupsin the prepolymer is from about 1.2 to about 2.0; (b) a neutralizingagent; and (c) a chain extender selected from the group consisting ofdiamines, triamines, and combinations thereof; and an aqueous visiblelight absorbing dye dispersion comprising a visible light absorbing dyethat is not reactive towards the polyisocyanate, wherein the visiblelight absorbing dye is not reactive towards the polyisocyanate, furtherwherein the encapsulated visible light absorbing dye dispersion has anaverage particle size of from about 20 nm to about 900 nm, a viscosityof from about 2 to about 150 cps at room temperature, and a surfacetension of from about 15 to about 65 dyn at room temperature.
 19. An inkjet ink composition comprising an encapsulated visible light absorbingdye dispersion consisting essentially of: a polyurethane dispersion thatis the reaction product of: (a) a urethane prepolymer having an averageweight molecular weight of from about 1,000 to about 20,000 that is thecatalyzed reaction product of: (i) a polyol; (ii) a polyisocyanate; and(iii) an internal surfactant; (b) a neutralizing agent; and (c) a chainextender selected from the group consisting of diamines, triamines, andcombinations thereof; and a visible light absorbing dye, wherein thevisible light absorbing dye is not reactive towards the polyisocyanate.20. The ink jet ink of claim 19, wherein the encapsulated visible lightabsorbing dye dispersion has an average particle size of from about 20nm to about 900 nm, a viscosity of from about 2 to about 150 cps at roomtemperature, and a surface tension of from about 15 to about 65 dyn atroom temperature.